1. Technical Field
The present invention relates to an electro-optical device suck as a liquid crystal device or the like. In addition, the invention further relates to an electronic apparatus that is provided with an electro-optical device. An example of a variety of electronic apparatuses to which the invention can be applied includes but not limited to a liquid crystal projector.
2. Related Art
In a typical configuration of an electro-optical device of the related art, a pixel electrode is provided at an open region of each pixel, whereas a transistor that functions as a switching element for switch-controlling the pixel electrode and a storage capacitor that temporarily retains/holds the electric potential of the pixel electrode are formed in a non-open region of each pixel. In a lamination structure formed over a substrate according to the configuration of an electro-optical device disclosed in JP-A-2005-45017 or Japanese Patent No. 3,141,860, a storage capacitor is formed at a layer that is not the same as the layer of a transistor.
In contrast, with an aim to simplify the manufacturing process of an electro-optical device, a storage capacitor having a so-called “planar structure” is disclosed in JP-A-10-10548, JP-A-2002-297060, JP-A-2002-149087, Japanese Patent No. 3,106,566, and Japanese Patent No. 3,307,144. In the planar structure disclosed in JP-A-10-10548, JP-A-2002-297060, JP-A-2002-149087, Japanese Patent No. 3,106,566, and Japanese Patent No. 3,307,144, one electrode of the storage capacitor and the semiconductor layer of a transistor are formed as the same single film. Specifically, in the planar structure disclosed in JP-A-2002-297060, Japanese Patent No. 3,106,566, and Japanese Patent No. 3,307,144, a storage capacitor is made up of a lower capacitor electrode that is made of the same film as the semiconductor layer of a transistor, an upper capacitor electrode that is made of the same film as the gate electrode of the transistor, and a dielectric film that is made of the same film as the gate insulation film of the transistor. In such a configuration, the dielectric film is deposited between the lower capacitor electrode and the upper capacitor electrode. On the other hand, in the planar structure disclosed in JP-A-10-10548 or JP-A-2002-149087, the lower capacitor electrode of a storage capacitor is made of the same film as a light-shielding film that is deposited below a semiconductor layer, whereas the upper capacitor electrode of the storage capacitor is made of the same film as the semiconductor layer.
If the area size of a non-open region is made smaller in order to achieve a high numerical aperture as viewed in two dimensions over a substrate when the planar structure of a storage capacitor according to the above-identified JP-A-2002-297060, Japanese Patent No. 3,106,566, and Japanese Patent No. 3,307,144 is adopted, there is an adverse possibility that the upper capacitor electrode thereof and a gate electrode are arrayed in close proximity to each other in a plan view. As a result thereof, there is a risk of a short-circuit failure that could occur between the upper capacitor electrode thereof and the gate electrode. In addition to such a disadvantage, according to the above-described layer structure, it is practically impossible, or at best difficult, to shut off any incident light beam that propagates toward the semiconductor layer through upper layers formed above the semiconductor layer by means of the upper capacitor electrode.
In the planar structure disclosed in the above-identified JP-A-10-10548, one capacitor electrode is made of the same film as a semiconductor layer whereas another capacitor electrode is formed above the semiconductor layer in such a manner that the above-mentioned one capacitor electrode and the above-mentioned another capacitor electrode are formed opposite to each other. Accordingly, in the planar structure disclosed in the above-identified JP-A-10-10548, a storage capacitor having a dual-layer structure is formed. If the planar structure disclosed in the above-identified JP-A-10-10548 is adopted, it is necessary to connect still another capacitor electrode that is made of the same film as a light-shielding film to a ground potential in order to prevent any leakage current from occurring. For this reason, in the planar structure disclosed in the above-identified JP-A-10-10548, it is practically impossible or at best difficult to achieve a small difference between the electric potential of the above-mentioned still another capacitor electrode that is made of the same film as the light-shielding film and the upper-layer capacitor electrode that is made of the same film as the semiconductor layer. Since it is not possible to achieve a small electric potential difference therebetween, it is practically impossible or at best difficult to make the thickness of a dielectric film small. Since it is impossible to provide a thin dielectric film therebetween, the planar structure disclosed in the above-identified JP-A-10-10548 has a disadvantage in that it is practically impossible or at best difficult to achieve a large capacitance value of a storage capacitor.
Moreover, if the planar structure disclosed in JP-A-10-10548 or JP-A-2002-149087 is adopted, it is practically impossible or at best difficult to shut off any incident light beam that propagates toward the semiconductor layer through upper layers formed above the semiconductor layer by means of the upper capacitor electrode; in like manner, it is practically impossible or at best difficult to shut off any incident light beam that propagates toward the semiconductor layer through lower layers formed below the semiconductor layer by means of the lower capacitor electrode. Therefore, the planar structure disclosed in JP-A-10-10548 or JP-A-2002-149087 has a disadvantage in that an optical leakage current could occur due to an incident light beam that reaches the semiconductor layer, resulting in degradation in image display quality.